The present disclosure relates generally to data transmission protocols in mobile communication systems and, more specifically, to systems and methods for reduced timeslot monitoring during data transmission.
As used herein, the terms “mobile station” (MS), “user agent,” and “user equipment” (UE) can refer to electronic devices such as mobile telephones, personal digital assistants, handheld or laptop computers, and similar devices that have network communications capabilities. In some configurations, UE may refer to a mobile, wireless device. Such UEs that are mobile, wireless devices may or may not include a subscriber identity module (SIM) card. The terms may also refer to devices that have similar capabilities but that are not readily transportable, such as desktop computers, set-top boxes, or network nodes.
A UE may operate in a wireless communication network that provides for high-speed data communications. For example, the UE may operate in accordance with Global System for Mobile Communications (GSM) and General Packet Radio Service (GPRS) technologies. Today, such a UE may further operate in accordance with Enhanced Data rates for GSM Evolution (EDGE), or Enhanced GPRS (EGPRS) or Enhanced GPRS Phase 2 (EGPRS2).
EDGE/EGPRS/EGPRS2 are examples of digital mobile communications technology that allows for increased data transmission rate and improved data transmission reliability. It is often classified as a 2.75G network technology. EDGE has been introduced into GSM networks around the world since approximately 2003, initially in North America. EDGE/EGPRS/EGPRS2 may be used in any packet-switched application, such as those involving an internet connection. High-speed data applications, such as video and other multimedia services, benefit from EGPRS' increased data capacity.
A UE operating in accordance with EGPRS/EGPRS2 may have multi-slot capability that enables them to use between one (1) and eight (8) time slots for data transfer. More timeslots may be used if a downlink dual carrier configuration is supported. Since uplink and downlink channels are reserved separately, various multi-slot resource configurations may be assigned in different directions. UEs may be categorized into two types based on the multi-slot class that it supports. For example, (1) Multi-slot Classes 1-12, 19-45 (Type 1) UEs have multi-slot capability in the uplink (UL) and downlink (DL) directions and may use this capability quasi-simultaneously (for example, by transmitting or receiving within the same time division multiple access (TDMA) frame). This group of multi-slot classes may use half duplex communication. The reason for this limitation may be explained by selecting, for example, multi-slot class 26. In this case, the maximum allowable number of timeslots in the UL is 4 and in the DL it is 8. Simultaneous transmission and reception of this number of timeslots is possible only if the UE is capable of transmitting and receiving at the same time. This particular group, however, does not have such capability and the specification limits their operation to half-duplex. However, (2) Multi-slot Class 13-18 (Type 2) UEs are the most advanced group of UE and have the capability to simultaneously transmit and receive (full duplex communication), requiring splitters, duplexers, and filters to separate transmit and receive paths.
Regardless of the particular type of UE, during operation, the UE is assigned timeslots during which the UE can communicate with the base station. An assignment contains a set of timeslots on one (or, for downlink dual carrier, two) channel(s). In the case of an uplink assignment this is the total set of timeslots that may be used by the UE for uplink transmissions; in the case of a downlink assignment, this is the total set of timeslots on which the network may send data to the UE. For any given radio block period, the network dynamically allocates resources and determines on which downlink timeslots or uplink timeslots the UE may receive and/or transmit data. In basic transmission time intervals (BTTI), a given radio block period includes 4 TDMA frames and each TDMA frame includes 8 timeslots. The allocation algorithm is implementation dependent, but may take account of the UE's multislot class (the maximum number of timeslots on which it can transmit/receive, and the time required to switch from transmit to receive and vice versa), and will usually take account of the amount of data the base station controller (BSC) expects the UE to receive/transmit.
Reduced transmission time intervals (RTTI) can be used and is a modification to the above structure where, instead of a radio block being transmitted as four bursts with each block sent in a particular timeslot over four TDMA frames, a radio block (containing essentially the same amount of information) is transmitted using two timeslots in two TDMA frames. This reduces the transmission time for a block and reduces the overall latency of the system. Accordingly, a “reduced radio block period” is 2 TDMA frames (approx. 10 ms) compared with a basic radio block period, which is 4 TDMA frames (approx. 20 ms).
Uplink allocations are signaled by the use of an uplink state flag (USF), which is a number between 0 and 7 (inclusive), and is signaled in every downlink radio block. As part of its uplink assignment, the UE is informed which USF(s) on which timeslot(s) indicate an uplink allocation for that UE. USFs are generally included in the headers of downlink blocks. In the case of RTTI, USFs may be coded across radio blocks across four TDMA frames, for example in the same manner as downlink BTTI radio blocks are sent (“BTTI USF mode”) or (using two timeslots) across two TDMA frames (“RTTI USF mode”).
In some communication standards, there are “m” timeslots assigned for reception and “n” timeslots assigned for transmission. Thus, for a multislot class type 1 UE, there may be Min(m,n,2) reception and transmission timeslots with the same timeslot number. For a multislot class type 2 UE, there may be Min(m,n) reception and transmission timeslots with the same timeslot number. In the case of downlink dual carrier configurations, if timeslots with the same timeslot number are assigned on both channels, in calculating the value of m they may be counted as one timeslot. As a result, where both downlink and uplink timeslots are assigned, if assigned a single timeslot in one direction and one or more timeslots in the opposite direction, the timeslot number of the first timeslot may be the same as one of the timeslot(s) in the opposite direction. Similarly, if assigned two or more uplink timeslots and two or more downlink timeslots, at least two of the uplink and downlink timeslots may have a common timeslot number. As a result, in uplink+downlink assignments, the timeslots that may be monitored for USFs and downlink data blocks are largely co-incident. In this implementation, assignments and allocations are essentially under the control of the network (for example, the BSC).
Depending upon the system, Extended Dynamic Allocation (EDA) may provide a mechanism to allow multiple uplink blocks to be allocated to a UE by means of a single USF indication. When this protocol is utilized for a temporary block flow (TBF), if a UE detects a USF allocating it an uplink block, it is also implicitly allocated uplink blocks sent in the same radio block period using all timeslots which are part of its assignment and which are numbered higher than that on which the USF was received.
During an ongoing packet data session in GPRS, a UE with an assigned downlink TBF is required to monitor all downlink timeslots in its assignment in case the network sends it data during those timeslots. Similarly, if a UE has an assigned uplink TBF, it is required to monitor all timeslots on which the uplink state flag (USF) could be sent to dynamically allocate uplink resources. If a UE has both uplink and downlink TBFs, the UE may monitor as many relevant downlink timeslots as possible, taking into account any uplink transmissions. The constant monitoring of assigned timeslots requires the expenditure of significant amounts of wasted energy in the case that either the network or the UE has nothing to send. This is particularly so when neither the network nor the UE has data to send. Although it is possible to release the assigned resources, this may lead to a user-perceived delay when further data is to be sent, since the resources may be re-established.